His 1981 book Livable Streets was described at the time by Grady Clay, the editor of the Landscape Architecture magazine, as "the most thorough and detailed work on urban streets to date".[1] It contained a comparison of three streets of similar morphology in San Francisco, which had different levels of car traffic: one with 2,000 vehicles per day, the others with 8,000 respectively 16,000 vehicles per day. His empirical research demonstrated that residents of the street with low car traffic volume had three times more friends than those living on the street with high car traffic.[1]

Appleyard is co-author with Allan Jacobs of the paper "Toward an Urban Design Manifesto".